1. Field of the Invention
The present invention relates to digital storage oscilloscopes, and in particular, to engine analyzers incorporating such oscilloscopes as display devices. The invention has particular application to dual-trace oscilloscopes operable in live and freeze modes.
2. Description of the Prior Art
It is known to provide digital oscilloscopes with multiple display traces (e.g., two), so that a number of waveforms can be simultaneously displayed. A dual-trace scope can typically be operated either in single-trace or dual-trace mode. It is also known to provide engine analyzers with display screens which essentially constitute digital oscilloscopes. Such analyzers acquire analog waveforms from an associated engine by means of pickup leads and then digitize the waveforms for storage in memory and display on the digital oscilloscope screen.
The horizontal scale (also called sweep) of an oscilloscope screen represents time. Broadly speaking, in a digital analyzer scope there are two types of sweeps: engine sweeps and fixed-time sweeps. Engine sweeps are of three types, cylinder sweep which display waveforms for a single cylinder cycle (the time between the firing of two consecutive cylinders in the firing order), and parade and raster sweeps for displaying a waveform over a complete engine cycle (the time between consecutive firings of the same cylinder). A parade sweep displays the cylinders spaced horizontally across the width of the screen and a raster sweep displays the cylinders stacked vertically one atop the other on the same time base. Engine sweeps are typically used to display waveforms related to cylinder ignition events. Fixed-time sweeps (e.g., 10 ms, 100 ms, etc.) display a fixed period of time across the width of the display screen, and are typically used to display waveforms other than primary and secondary ignition waveforms.
It is known in prior digital engine analyzers to operate the analyzer in either ignition scope mode or standard lab scope mode. The ignition scope mode is normally used for analyzing primary and secondary ignition waveforms. The lab scope mode is used for analyzing waveforms other than primary and secondary ignition waveforms, the display of which other waveforms utilizes a fixed-time sweep.
Digital engine analyzers with oscilloscope displays typically have two modes of operation, viz., live and freeze. In the live mode, one or more selected input signals are repeatedly sampled by a data acquisition system and the resulting digitized waveform data is displayed on the screen of the oscilloscope and saved in memory. When the freeze mode is activated, data acquisition is suspended and the most recently-displayed section of waveform data remains xe2x80x9cfrozenxe2x80x9d on the screen. At this point the operator can review previously acquired waveform data that has been saved in memory by recalling it from memory and displaying it on the screen.
It is also known to provide an engine analyzer with a database of reference information which includes a library of signal waveform patterns, which may include generic standard or reference patterns, known xe2x80x9cgoodxe2x80x9d patterns for a properly operating engine, or known xe2x80x9cbadxe2x80x9d patterns which typify known specific trouble conditions. Library patterns can also be called from memory and displayed on a trace of the oscilloscope screen.
When prior engine analyzers are operating in a freeze mode, there is little that the operator can do to manipulate or reconfigure the waveform data displayed on the screen. In some analyzers it is possible for the operator to change the scale of a frozen waveform and, in some general purpose laboratory oscilloscopes, it is known to permit alteration of a fixed-time sweep for the display of a frozen waveform. But that is about the limit of an operator""s control of frozen waveforms.
It is a general object of the invention to provide an improved digital oscilloscope which avoids the disadvantages of prior oscilloscopes while affording additional structural and operating advantages.
An important feature of the invention is the provision of an oscilloscope of the type set forth, which is operable in single-trace and dual-trace and in live and freeze modes, and which permits an operator to reconfigure a frozen screen display format by altering any of a number of different display parameters.
In connection with the foregoing feature, a further feature of the invention is the provision of an apparatus of the type set forth, wherein the parameters which can be altered include the number of traces in the display format, the particular signal displayed on a trace, scale of the display and the zero-offset point of the scale.
Yet another feature of the invention is the provision of an apparatus of the type set forth embodied in an engine analyzer for monitoring waveforms of multi-cylinder internal combustion engines, wherein the parameters which can be altered include the engine sweep of the waveform display and, in the case of a cylinder sweep, the cylinder displayed.
These and other features of the invention are attained by providing apparatus for monitoring analog input waveforms comprising: waveform acquisition means including signal pickup leads adapted to be coupled to an associated source for respectively receiving different analog input signals and generating digitized waveform data representative of such analog signals, memory means for storing digitized waveform data, an oscilloscope display device having a display screen for displaying stored waveform data from one or more input signals in a screen display format which includes one or more waveform representations on one or more traces, and processing means coupled to the waveform acquisition means and to the memory means and to the display device and operable under stored program control for controlling storage and display of waveform data, the processing means including freeze control means for selectively operating the display device in either a live mode in which acquired waveform data is displayed substantially currently as acquired and a freeze mode in which a screen display format is frozen on the screen, the freeze control means including means selectively operable for reconfiguring a frozen screen display format by altering the number of traces and/or the signal displayed on a trace.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.